In conventional technologies, in order to establish a data channel between two terminals over an IP network to perform so-called peer-to-peer communications, various preparation activities are necessary such as name registration to DNS, setting and management of FW (fire wall) for ensuring security, obtaining public-key certificates and the like. For a terminal to perform encrypted peer-to-peer communications with many terminals through mutual authentication, it is necessary for the terminal to obtain public-key certificates of all other terminals or IDs and passwords of all other terminals.
As mentioned above, according to the conventional technologies, complicated activities are necessary to establish a secure data channel between two terminals over an IP network. In addition to that, since names and addresses of terminals are to be registered in an open DNS, there is a problem in that unauthorized access may occur and that data in the open DNS may be tampered with.
A mechanism for establishing a pseudo peer-to-peer data channel between two terminals is proposed. In the mechanism, a mediating server is introduced between the terminals. The mediating server terminates a data channel from a terminal at one endpoint as a proxy and terminates a data channel from a terminal at another endpoint, and connects the data channels. However, according to this method, since all data exchanged between the terminals pass through the mediating server, there is a problem in that a heavy work load is placed on the mediating server. In addition, there is a problem in that real-time access to a home terminal cannot be realized by the mechanism. Japanese Laid-Open Patent Application No. 2002-208921 discloses a technology related to establishing a secure channel.